Printed circuit boards with tracks of this type are required for electronic circuits in which, as a rule, different electronic components have to be interconnected in a certain manner. The steps of drilling through the printed circuit boards equipped with tracks at the points where the components are connected and of inserting the wire leads of the respective components into the bore holes and of soldering them to the tracks is known in the art. Furthermore, the use of the so-called surface-mounted devices (SMD), in which the devices are initially glued onto the printed circuit board, by placing the connecting points on the projected tracks and then soldering them together, is also known in the art. This technique uses smaller components, which are arranged in a flat configuration to save space. In addition, the latter manufacturing process is less costly and expensive, due to the elimination of the drilling procedure.
Since many of the available components are only offered in SMD technology for certain purposes and since these components are already used for reasons of cost, it is often necessary to combine different kinds of electronic components on the same printed circuit board to form a mixed assembly.
Printed circuit boards of this kind of mixed assembly are known to the art and are described in a brochure entitled "Siemens-Teststrategie und Prufverfahren four SMD-Gruppen", which translated means "Siemens Test Strategy and Testing Procedure for SMD Assemblies", issue No. 53 d 7/86, by Siemens Aktiengesellshaft (AB). This brochure describes printed circuit boards which have hard-wired components mounted on the one or upper side thereof. These printed circuit boards are normally equipped with tracks in which the connecting points are provided with bore holes into which the conductive leads of the hard-wired components are inserted and soldered. The SMD components, on the other hand, are normally glued to the underside of the printed circuit boart. The SMD components are glued on by placing the contact surfaces of the components on the projected tracks. The entire printed circuit board assembly can be soldered in a single procedure by flow soldering. The SMD components are immersed into the soldering bath as a complete assembly. During this flow soldering process, it is possible that all of the components may be briefly touched by hot molten solder on all sides. However, since some SMD components cannot withstand a thermal shock or stress of this intensity, a soldering assembly of this kind on a printed circuit board may not be always possible.